JPH04178954A - Tape speed detector for video tape recorder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a tape speed detection device for a helical scan video tape recorder that records video tracks obliquely to the longitudinal direction of the tape.

BACKGROUND OF THE INVENTION In recent years, variable speed playback technology has advanced in video tape recorders, and as a result, a highly accurate tape speed detection device is required.

The configuration of a conventional tape speed detection device will be described below with reference to FIG.

In the figure, the conventional tape speed detection device has input terminal 1,
It has a frequency/voltage converter 2 and an output terminal 3. An FG signal from a capstan (not shown) is input to input terminal 1, and a capstan FG signal is input from pressure terminal 3.
It is possible to obtain a voltage proportional to the frequency of the tape, that is, a voltage proportional to the tape speed.

Problems to be Solved by the Invention In such conventional tape speed detection devices, the inspection accuracy is limited by the resolution of the capstan FG, and there is a problem in that it is difficult to detect tape speed information with high accuracy.

The present invention solves the above problems, and
It is an object of the present invention to provide a highly accurate tape speed detection device for a recorder.

Means for Solving the Problems In order to achieve the above object, the present invention provides a clock separation circuit that separates and outputs a clock from a playback signal of a video tape recorder, and a reference frequency. a multiplier that inputs and multiplies the clock and the reference frequency; and a low-pass filter that inputs the pressure of the multiplier and outputs a frequency component of the difference between the clock and the reference frequency. , a frequency/voltage converter that inputs the output of the filter and outputs a voltage corresponding to the frequency, and the output of the converter is a voltage proportional to the tape speed, as a speed detection device for a video tape recorder, In addition, as a second problem solving means, a burst separation circuit that separates and outputs a burst signal from a playback signal of a video tape recorder, a reference frequency oscillator that applies pressure to a reference frequency, and a combination of the burst signal and the reference frequency are provided. a multiplier that inputs pressure and multiplies it; a low-pass filter that inputs the pressure of the multiplier and compresses the frequency component of the difference between the burst signal and a reference frequency; and a low-pass filter that inputs the output of the filter to correspond to the frequency. A speed detection device for a video tape recorder is provided with a frequency/voltage converter that outputs a voltage, and the output of the converter is a voltage proportional to the tape speed.

In the tape speed detection device of the first problem solving means, the multiplier multiplies the clock of the reproduced signal separated by the clock separation circuit and the reference frequency of the reference oscillator to obtain the sum and difference frequencies. is generated and a low-pass filter outputs the frequency of said difference.

A frequency/voltage converter converts the difference frequency into a voltage. This voltage is proportional to the tape speed. Also,
In the tape speed detection device of the second means for solving the problem, a burst signal of a reproduced signal is used instead of a clock.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a video tape recorder according to an embodiment of the present invention.

In the figure, the tape speed detection device includes an input terminal 4, a clock separation circuit 5, a reference frequency oscillator 6, a multiplier 7, a low
By pass filter 8, frequency/voltage converter 9 and output terminal 10! llll! It will be done. The above components and their operations will be explained below.

The input terminal 4 receives a video track playback signal. The reproduced clock signal of the video track is separated by the clock separation circuit 5. The separated reproduced clock signal is input to a multiplier 7.

On the other hand, the reference clock signal obtained by the reference station wave number oscillator 6 is also input to the multiplier 7. Here, if the frequency of the reproduced clock signal is f and the frequency of the reference clock signal is 10, the output signals of the multiplier 7 are (f+10) and (f
-10) frequency component. The output signal of the multiplier 7 is input to a low pass filter 8, where the frequency component of (f+f0) is removed and only the frequency component of (f−fo>) remains.The output signal of the low pass filter 8 is It is input to the voltage converter 9, and from the pressure terminal 10, the frequency (f-f
A voltage proportional to o) is obtained.

By the way, when the tape speed changes, the relative speed between the tape and the head changes, and the frequency f of the reproduced clock signal also changes. Therefore, the frequency obtained from the output terminal 10 (
The voltage proportional to f-fo) is nothing but the voltage proportional to tape speed.

This voltage output has higher speed resolution than the tape speed information obtained from the conventional FG multiplied signal. For example, while the conventional FG multiplied signal frequency is about 2 KHz, the clock of the reproduction signal of the digital recording method is about 45, and a resolution about 20 times higher can be obtained.

As described above, according to the tape speed detection device for a video tape L/coder according to an embodiment of the present invention, in order to achieve the above object, the present invention separates the clock from the playback signal of the video tape recorder. A clock separation circuit to output,
a reference frequency oscillator that applies pressure to the reference frequency; a oscillator that inputs and multiplies the clock and the reference frequency; and inputs the output of the multiplier to apply pressure to the frequency component of the difference between the clock and the reference frequency. A video tape recorder comprising a low bass filter and a frequency/voltage converter that inputs the output of the filter and applies a voltage corresponding to the frequency, and the output of the converter is a voltage proportional to the tape speed. By using a speed detection device, the tape speed can be detected with high resolution and accuracy.

It goes without saying that in an analog recording type video tape recorder, the same effect can be obtained by using a burst signal in a playback signal.

Further, the reference frequency can be set so that the difference frequency does not become zero within the range of change of the clock or burst signal frequency. For example, it is set above the upper limit or below the lower limit of the variation range of the clock or burst signal frequency. With this setting, it is possible to accurately check whether the tape speed is plano or negative relative to the standard.

Effects of the Invention As is clear from the above embodiments, the present invention includes a clock separation circuit that separates and applies a clock from a playback signal of a video tape recorder, a reference frequency oscillator that applies a reference frequency, and a a multiplier that inputs and multiplies the reference frequency; a low bass filter that inputs the output of the multiplier and outputs a frequency component of the difference between the clock and the reference frequency; and a low bass filter that inputs the output of the filter. The resolution can be improved by providing a frequency/voltage converter that applies a voltage corresponding to the frequency, and making the output of the converter a voltage proportional to the tape speed. The tape speed can be detected with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a tape speed detection device for a video tape recorder according to an embodiment of the present invention, and FIG.
The figure is a schematic diagram showing the configuration of a conventional tape speed detection device for a video tape recorder. 5... Clock separation circuit, 6... Reference frequency oscillation! , 7... Multiplier, 8...
Low-pass filter, 9... Frequency/voltage converter.

Claims (2)

[Claims] (1) A clock separation circuit that separates and outputs a clock from a playback signal of a video tape recorder, a reference frequency oscillator that outputs a reference frequency, and a multiplier that inputs and multiplies the clock and the reference frequency. , a low pass filter that inputs the output of the multiplier and outputs a frequency component of the difference between the clock and a reference frequency, and a frequency/voltage converter that inputs the output of the filter and outputs a voltage corresponding to the frequency. A speed detecting device for a video tape recorder, wherein the converter outputs a voltage proportional to the tape speed. (2) A burst separation circuit that separates and outputs a burst signal from a playback signal of a video tape recorder, a reference frequency oscillator that outputs a reference frequency, and a multiplier that inputs and multiplies the burst signal and the reference frequency. a low-pass filter that inputs the output of the multiplier and outputs a frequency component of the difference between the burst signal and a reference frequency; and a frequency/low-pass filter that inputs the output of the filter and outputs a voltage corresponding to the frequency. A speed detection device for a video tape recorder, comprising a voltage converter, the output of the converter being a voltage proportional to the tape speed.